Optical components must be tested prior to their utilization. Conventionally, the testing of optical components is carried out by trained personnel by visual manual inspection. This approach is not quantitative in nature, and thus can not be carried out objectively and reliably. The performance varies with different inspectors and with the same inspector from time to time.
Efforts have been made to develop methods and devices for automatic and objective testing of transparent optical components. The following patents deal with subject matter: DE Pat. No. 3620146 (U.S. Pat. No. 4,841,139); DE Pat. No. 3620108 (U.S. Pat. No. 4,822,165); DE Pat. No. 3620129 (U.S. Pat. No. 4,815,844); DD Pat. No. 241120; U.S. Pat. No. 3,988,068; UK Pat. No. 34851/72 (U.S. Pat. No. 3,892,494).
These have significant drawbacks. The proposed solutions in these patents are not cost effective in the sense that they are too complex and slow for use in mass production lines. Systems that utilize complex scanning means are too slow to inspect hundreds of lenses per hour, as required in such lines.
Another problem arises from sensitivity to various lens parameters. The lenses may be positive or negative, spherical, cylindrical or both, aspheric and progressive. Most solutions have difficulties in adapting to different batches of lenses that have different geometrical properties, using different illumination geometries for each batch, thus consuming time in arranging the set up between different batches.
Yet, a serious problem arises from the illumination methodology itself, patents using light sources with characteristics that are different in nature from the recommendation in the various cosmetic standards, lead to differences in the defects appearance in respect to their appearance in daily use of lenses, thus causing to a serious reliability problem by producing artifacts that are not detectable in daily use. Furthermore, some of the illumination methods are sensitive to different defects locations causing difficulties in simultaneously detecting defects in both faces and inside the lens and therefore resulting in non homogeneous yield.
The present patent overcomes these difficulties and shortcomings of the said previous patents.